Water Heating

Fact: Water heating is the third largest energy expense in your home (after space heating and cooling). It typically accounts for about 14% of your utility bill. You can reduce energy consumption by 50%.

  • Best Features:
  • If your gas water heater is more than 10 years old, its efficiency is probably no higher than 50%. It would be cost-effective to replace your old water heater with a new, higher-efficiency model. In selecting your water heater, keep these tips in mind:

  • Select the appropriate first-hour rating (FHR).

  • Look for the Energy Guide label.

  • If you are in a moderate climate (i.e., with relatively low heating loads), consider a Heat Pump Water Heater (HPWH).

  • Owning a larger tank doesn't necessarily mean a higher FHR.

  • Everything else being equal, select a water heater with the highest energy factor (EF).

There are a number of technologies available to heat water efficiently. However, before implementing these technologies, it's important to first reduce hot water use with water-saving fixtures and appliances. Conserving water and heating it efficiently should be addressed during your whole-building design process. Water heating technologies include:

  • Conventional Water Heating Efficiency

  • Drain water Heat Recovery

  • Heat Pump Water Heating

  • Demand (Tankless or Instantaneous) Water Systems

  • Solar Hot Water Heating

  • There are four ways to cut your water heating bills:
  • Use less hot water

  • Turn down the thermostat on your water heater

  • Insulate your water heater

  • Buy a new, more efficient water heater.


A family of four, each showering for 5 minutes a day, uses 700 gallons of water a week; this is enough for a 3-year supply of drinking water for one person. You can cut that amount in half simply by using low-flow aerating showerheads and faucets. These tips will help take the guesswork out:

  • Install aerators in faucets and low-flow showerheads so you can reduce your hot water consumption by half.

  • Lower the thermostat(s) on your water heater to 120°F.

  • Do not install the water heater in an unheated basement, whenever possible.

  • Locate the water heater where the length of piping runs to your bathroom and kitchen is minimized.

Solar Water Heaters: See section Solar Water Heaters. If you heat with electricity and you have an unshaded, south-facing location (such as a roof) on your property, consider installing a solar water heater. More than 1.5 million homes and businesses in the United States have invested in solar water heating systems and over 94% of these customers consider the systems a good investment. Solar water heating systems are also good for the environment. Solar water heaters avoid the harmful greenhouse gas emissions associated with electricity production. During a 20 year period, one solar water heater can avoid over 50 tons of carbon dioxide emissions.

Solar water heating is a renewable energy technology that is well proven and readily available and has considerable potential for application at Federal facilities. Solar water-heating systems can be used effectively throughout the country and most facilities will have an appropriate near-south-facing roof or nearby unshaded grounds for installation of a collector. A variety of types of systems are available and suitable for many applications. For example, low-temperature unglazed systems can heat swimming pools and associated hot tubs or spas, saving money on conventional heating or extending the swimming season. In mild climates, passive systems without pumps or electronic controllers can provide low-maintenance hot water for facilities with limited or expensive utility service. High-temperature parabolic-trough systems can economically provide hot water to jails, hospitals, and other facilities in areas with good solar resources that consistently use large volumes of hot water. And active flat-plate systems can service any facility in any area with electric or otherwise expensive conventional water heating.

When shopping for a solar water heater, watch for systems certified by the Solar Rating and Certification Corporation (SRCC) or the Florida Solar Energy Center (FSEC).

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Figure 40: Hot Water Usage - (based on national averages)
The typical U.S. homeowner's water consumption by place of use.

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